At what point during the execution of the following program will there be the largest number of activation records on the stack?

void f0() { } void f1() { } void f2() { f1(); } void f3() { f2(); } void f4() { f3(); } int main() { for (int i=0; i<100; ++i) f0(); f2(); f3(); f4(); }

When f0() is running.

When f1() is running.

when f2() is running.

when f3() is running.

when f4() is running.